The cragoe L function for the viscosity of oils under pressure at certain temperatures

Abstract

The Cragoe L function for the viscosity of oils has been computed for 12. representative petroleum oils over a pressure range of 28,000 ψ and a temperature range from 100° to 210°F. It has been shown that, on the basis of the viscosity measurements for these new oils, the pressure coefficient β is not approximately constant for a given oil over a low pressure range, as supposed by Cragoe, but is a function of pressure, and, to a lesser extent, a function of temperature. The magnitude of β has been found to be dependent on the type of oil, e.g., whether the type is paraffinic or naphthenic and aromatic; and its pressure and temperature variation is likewise different for the different types of oils. The defining equation for L has been interpreted in terms of current reaction rate theory, and it has been demonstrated that volume effects alone are not adequate to account for the observed viscosity effects under pressure. It has been suggested that orientation effects during viscous flow are probably responsible for the discrepancies now existing between measurement and theory. The writer acknowledges the assistance of his wife, Evelyn T. Dow, who carried out many of the computations.